Touch Fastener

ABSTRACT

The invention relates to a touch fastener with a plurality of interspaced bonding elements that are arranged on the backing, each element having a head ( 12 ) that is connected to the backing by means of a stem ( 14 ). To allow the head ( 12 ) to always remain fastened to a body in the immediate vicinity, even if the backing is axially displaced over a predeterminable distance on a plane running parallel to said body, the head ( 12 ) consists of a disc with a diameter that is greater than the diameter at any point on the stem ( 14 ), the latter being conical and connected to the disc in an articulated manner by means of an articulated part ( 16 ).

The invention relates to a touch fastener having a plurality of bondingelements which are spaced relative to one another, which are located ona backing, and which each have a head which is connected to the backingby means of a stem.

DO 2004/105536 A1 discloses a touch fastener in which the free ends ofthe stems of the individual bonding elements are provided with aplurality of individual fibers, the diameter of the respective fibersbeing chosen to be very thin so that on the free end of each individualfiber only a very small contact surface ranging from 0.2 to 0.5 μm isavailable.

These orders of magnitude, which in preferred embodiments can also be inthe nanometer range, enable interaction with a corresponding body in thevicinity on which the touch fastener is to be attached, by means ofso-called van-der-Waals forces which are classically regarded as asubgroup of adhesion. The conventional touch fastener has goodconnection properties, but is tied to a correspondingly costlyproduction process.

This also applies to a touch fastener according to the teaching ofpublication WO 01/49776 A2 which provides indications to one skilled inthe art to use parts of the foot structure of a gecko directly asbiological material, or to artificially imitate it, this adhesivestructure consisting of a plurality of so-called spatulae componentswhich are each divided into a plurality of individual filaments in theform of a bent cylindrical fastener-element on the free end.

Conversely, for simplified production, DE 102 23 234 B4 has alreadyproposed a method for surface modification of an object, in the form ofa fastener part with the objective of increasing the adhesion capacityof the bonding element. For this purpose, the free surface is subjectedto structuring in order to form a plurality of projections, which areeach provided with a foot part and a head part, the head part having aface surface which is oriented away from the surface and each projectionbeing formed with a size such that all face surfaces have the samevertical height over the surface. This yields an adherent contactsurface interrupted by mutual distances between the face surfaces, thefoot parts of the projections being tilted relative to the surfacenormals of the surface.

Although it is possible with this known solution to make available theimplementation of detachable bonding connections for an extended rangeof materials, with increased adhesion capacity and the possibility ofenabling the setting of predetermined adhesion forces or properties;however, based on the relatively rigid arrangement between the head andbacking by means of the optionally tilted stems, there is stillopportunity for improved solutions.

On the basis of this prior art, the object of the invention is tofurther improve these known solutions such that improved adherence andfastening action are created for the respective touch fastener, with thesimultaneous possibility of being able to produce these systemseconomically and reliably. This object is achieved by a touch fastenerwith the features of claim 1 in its entirety.

In that, as specified in the characterizing part of claim 1, the headconsists of a head plate whose diameter is greater than the diameter atany point of the stem, which stem, made conically, is linked to the headplate by means of an articulation part, the result is that the head ineach instance remains adhering to a body in the vicinity, even if thebacking should be displaced axially in the plane-parallel direction tothis body by a predefinable amount. As a result of coupling by means ofthe articulation parts, the stems can tilt in the oblique directionwithin a predefinable framework, without this adversely affecting thecoupling of the head relative to the body in the vicinity. Since,moreover, the head with the head plate can have a very large diameter,the possibility of adhering to the indicated body in the vicinity isimproved.

In particular, when vibrations occur in which the backing executesshort-stroke vibrations relative to the body in the vicinity, the touchfastener according to the invention is an especially good connectionsolution. The coupling which has been improved in this way even prevailswhen the respective stem relative to the head from the outset assumes apredefinable alignment in the form of a tilt relative to the vertical.

Due to the conical arrangement of the stem elements which widen in thedirection of the backing, an independent component need not be formedfor the articulation site; rather the articulation site can be formeddue to the direct transition of the conically tapering tip of the stemor its end into the head. Since the respective-stem thus has itsgreatest diameter in the region of the transition to the backing, in thedirection of the tapering stem end the intermediate space betweenadjacent bonding elements is increased so that at this site increaseddistribution space or embedding space for the heads with their headplates is available. In this way the diameter ranges for the heads canbe dramatically increased unhindered by the remaining stem structure sothat in this respect improved adhesion over an enlarged contact surfaceis achieved. This structure also results in reliable operation of thetouch fastener which can be repeatedly detached. Furthermore thearrangement according to the invention can be economically produced inlarge numbers.

Other advantageous embodiments of the touch fastener according to theinvention are the subject matter of the other dependent claims.

The touch fastener according to the invention is detailed below usingone embodiment as shown in the drawings. The figures are schematic andnot to scale.

FIG. 1 shows in a perspective plan view an extract from a touch fastenerwith a plurality of bonding elements,

FIG. 2 shows in a section an individual bonding element as shown in FIG.1,

FIG. 3 shows a representation corresponding to FIG. 2, however, with anindividual bonding element, once in a vertical alignment, once in anoblique arrangement and without the backing;

FIGS. 4 to 6 show other embodiments of the solution according to theinvention with different head shapes, viewed in cross section.

The orders of magnitude addressed with the touch fastener should sufficein the geometrical implementation and are designed such that interactionwith a corresponding part, whether in the form of another touchfastener, or in the form of the surface of a body in the vicinity onwhich the touch fastener according to the invention is to be fixed, canpreferably take place by means of so-called van-der-Waals forces.So-called van-der-Waals forces which constitute a subgroup of adhesionare formed because the negatively charged electrons which are swirlingaround the positive nucleus in an atom are briefly concentrated on oneside. For this reason the atom on this side is temporarily negativelycharged, on the other side conversely it is positively charged. Thisalso influences adjacent atoms; in this case the atoms along the top ofthe support surface of the head, with the result that the supportsurface of the head, depending on which charge it receives, is attractedeither by the positive atoms or the negative atoms of the respectiveopposite surface of the body in the vicinity.

The larger the resulting contact surfaces are in total, the stronger theforces which arise, so that the resulting large-dimensioned head supportsurfaces which arise as a result of the conically tapering stem ends arefavorable for achieving strong van-der-Waals forces. Although thevan-der-Waals forces are among the weakest forces in nature, the effectis sufficient to achieve relatively high fastening forces, especiallyconsidering that there can be several thousand bonding elements on theextremely small space of the backing. If the surface of the respectivehead should be chemically modified in a corresponding manner, a truechemical bond as the adhesion connection is conceivable.

The touch fastener shown in FIG. 1, for the purposes of this invention,can be obtained, for example, according to a micro-replication processas described in DE 196 46 318 A1. The prior art process is used toproduce a touch fastener with a plurality of interlocking means made inone piece with the backing 10 in the form of stems 14 which have heads12, in which preferably a thermoplastic in the plastic or liquid stateis delivered to the gap between a compression roll and a shaping roll,the shaping roll being provided with a screen, with cavities open to theinterior and exterior, and the two rolls for the production process aredriven in opposite directions so that the backing material is formed inthe gap between the rolls with the formation of the backing 10. Sincefor the touch fastener according to the invention the stems 14 are to bemade conical, in this respect the screen cross section is matched to theexterior contour of the respective support stem 14, in particular, thescreen cross section uniformly tapers conically in the direction of theinterior of the roll.

Another possibility for obtaining the fastener system shown in thefigures is described in DE 100 65 819 C1. In this known method forproducing touch fasteners, a backing material in at least one partialregion of its surface is provided with touch fastener elements orbonding elements which project from its plane, in which a plasticmaterial which forms the elements is applied to the backing element asthe backing 10, the elements being made without a shaping tool at leastin one partial region in which the plastic material is deposited bymeans of at least one application device in successively delivereddroplets. Although the application device yields plastic material with adroplet volume of only a few picoliters via its nozzle, in this way ahigh-speed process can be implemented such that a touch fastener asshown in FIG. 1 is obtained in an extremely short period of time. Thismethod also makes it possible, in particular, to produce individualbonding elements as shown in FIG. 3 which each consist of a head 12 anda conical stem 14 with an articulation part 16. In turn these bondingelements can then be applied in a plurality of backings 10 of any form,for example, by cementing or melting on, this backing 10 then notneeding to have a configuration which runs flat, but may definitelyfollow curved paths with convex or concave radii (not shown).

Another option for producing the touch fastener according to theinvention may consist in that a thin plastic film is applied, forexample, doctored on, onto the free tapering stem end 14 in order tothen clip it, for example, by means of a laser, to obtain the desiredgeometry of the respective head 12. Films can also be applied in thisway for the backing 10.

The backing 10 as well as the heads 12 and the tapering stems 14 withintegrated articulation coupling consist preferably of a plasticmaterial which is chosen in particular from the group of acrylates suchas polymethacrylates, polyethylenes, polypropylenes, polyoxymethylenes,polyvinylidene fluoride, polymethylpentene,poly(ethylene)-chlorotrifluoroethylene, polyvinyl chloride, polyethyleneoxide, polyethylene terephthalate, polybutylene terephthalate, nylon 6,nylon 6.6, and polybutene.

Essentially, plastics with long chains of molecules and good orientationbehavior, as well as plastic materials with thixotropic behavior can beused especially effectively. Thixotropic behavior for the purposes ofthe invention in this connection is to denote the reduction ofstructural thickness during the shear loading phase and its more or lessa prompt but complete restoration during the following rest phase. Thisbreakdown/restoration cycle is a completely reversible process andthixotropic behavior can be defined as a time-dependent behavior.

Furthermore, plastic materials have proven favorable in which theviscosity measured with a rotational viscosimeter ranges from 7,000 to15,000 mPas; but preferably it has a value of approx. 10,000 mPas at ashear rate of 10 l/sec. For the purposes of a self-cleaning surface ithas moreover proven favorable to use plastic materials whose contactangle has at least a value of greater than 60 degrees as a result of itssurface energy for wetting with water. Under certain circumstances, thissurface energy can be further changed by subsequent treatment processes.

With respect to the aforementioned requirements, an especiallyinteresting representative of suitable plastic materials is polyvinylsiloxane, and the use of this plastic can be provided in particular forforming the heads 12 and their free surface side.

For the sake of clarity, the individual bonding elements in FIG. 1 areshown arranged spaced relatively far apart from one another. In reality,these bonding elements consisting of the stem 14, articulation site 16,and head 12 lie tightly against one another. Thus 10,000 to 20,000 ofthese elements per square centimeter can be located on the homogenousbacking 10. A uniform arrangement is preferred in which all bondingelements have the same distance to one another; but there is also thepossibility of irregular arrangements here or those in pattern form(circular, stem-shaped, ellipsoidal, etc.).

The heads 12 which are disc-shaped in terms of the exterior contour canalso have other shapes, for example, can be made elliptical or inpolygonal form, the hexagonal form having been found to be especiallyfavorable, also relative to the screen shaping process; the same appliesto the stems 14. The conicity for the respective stem 14 is at least onedegree of oblique tilt relative to horizontal; but is preferably approx.2.5 to 5 degrees in order in this way to be able to obtain slender stemelements. The articulation site 16 itself as shown in FIG. 2 has adiameter from approx. 1 to 5 μm, preferably 2 μm, this diameter rangebeing shown in FIG. 2 as Z2.

In the embodiment shown in FIG. 2, the conical stem 14 as a molded partis connected in one piece to the backing 10; but here it is alsopossible to produce the connection of the stem 14 to the backing 10 viaa cement connection (not detailed) in the same size range. The thicknessof the backing 10 is shown in FIG. 2 with the opposing arrows W and interms of magnitude corresponds to the indicated size Z2. In particular,when the bonding element as shown in FIG. 3 is produced without backing10 and is connected to it only later, for example, by means of a cementor melt connection method, the backing 10 can also be made larger interms of the thickness W. On its end facing away from the articulationsite 16 the conical stem has a thickness Z1 from 5 to 25 μm, preferablyfrom approx. 10 to 20 μm, and the diameter Y of the head 12 is in turn,depending on the stem geometry, 30 to 100 μm, preferably approx. 40 μm.The head 12 in terms of its thickness X is chosen to be exceptionallynarrow-lipped and the values here can be <1 μm. For an embodiment whichis not shown, it is also provided that, originating from the transitionregion of the head 12, from the stem 14 to the exterior the lattertapers in terms of width and ends in an annular end edge. Especiallyhigh holding forces for the head 12 can be expected for thenarrow-lipped feature which tapers in this way.

The purpose of FIG. 3 is to illustrate in particular a detachment of thehead 12 as a peeling motion from the body 18 in the vicinity, for which,when the stem 14 is tilted around the articulation part by an angle a ofapprox. 20° relative to the vertical 20, the peeling motion takes place,i.e., the edge of the head 12 which is the left edge viewed in thedirection of looking at FIG. 3 begins to detach over the contact surface22 of the head 12 as a rolling motion. Depending on the concept of thetouch fastening element this angle a can also be more than 20°, inparticular at least 40°. If in the initial state the stem 14 is notlocated parallel to the vertical 20, but rather, running obliquely,already assumes a starting angle a, that is, the tapered end of the stem14 ends in an oblique arrangement on the otherwise flat head plate ofthe head 12, for a detachment motion in turn a corresponding angleoffset can be expected which, however, is then lower this time than fora vertical arrangement of the stems 14 relative to the head plate of thehead 12.

As shown, the head plate can be made flat and accordingly can haveessentially a uniform thickness; but it is also possible to implementother cross sectional shapes on head plates within the framework of thesolution according to the invention. In another embodiment, as shown inFIG. 4, the head plate viewed in cross section is made as a double wedgeshape, i.e., proceeding from the middle in the region of the stem 14 thehead plate narrows to both sides, along bevels which taper toward oneanother. In the embodiment as shown in FIG. 5, a single wedge is formedwhich on its one side has the greatest thickness and on the oppositeside has the smallest thickness. In the illustrated embodiment only thetop is tilted; but here it is also possible to allow the top andunderside to taper toward one another to form a wedge. In the embodimentas shown in FIG. 6, in contrast to the above described solutions, thestem 14 is arranged off-center on the underside of the head plate of thehead 12, which plate is made flat. Instead of the head plate which ismade flat, in the embodiment as shown in FIG. 6, it can also have othershapes, in particular the wedge cross sectional shapes as shown in FIGS.4 and 5. If a tilted wedge shape is used for the head plate, the obliquesurfaces are tilted between 5° to 15°, preferably by 10°, so thatdepending on the peeling direction the associated angle a can be set, inparticular, can be enlarged. The sharp-edged transitions shown in thefigures between the backing band, the stem 14 and the head 12 arepreferably round, in particular the transition between the underside ofhead 12 and stem 14. Furthermore, the radial outside edges of the head12, at least partially, can likewise be provided with the correspondingrounding; this can simplify production.

1. A touch fastener with a plurality of bonding elements which arespaced relative to one another, which are located on a backing (10), andwhich each have a head (12) which is connected to the backing (10) bymeans of a stem (14), characterized in that the head (12) consists of ahead plate with a diameter which is greater than the diameter at anypoint of the stem (14) which, made conically, is linked to the headplate by means of an articulation part (16).
 2. The touch fasteneraccording to claim 1, wherein the head plate has essentially a uniformthickness or, viewed in cross section, a wedge or double wedge shape,and wherein its outer periphery follows a curved, in particular circularpath, or is polygonal, in particular hexagonal.
 3. The touch fasteneraccording to claim 1, wherein the contact surface (22) of the head (12)enables redetachable adherence to a body in the vicinity, by means ofadhesion force.
 4. The touch fastener according to claim 3, wherein thebacking (10) is connected integrally to the bonding elements.
 5. Thetouch fastener according to claim 1, wherein in the initial state theheads (14) are essentially vertically upright on the respectiveassignable stems (12).
 6. The touch fastener according to claim 4,wherein detachment of the head (12) takes place as a peeling motion froma body (18) in the vicinity when the stem (14) is tilted around thearticulation part (16) by an angle (a) of at least 20°, preferably of atleast 40° relative to the vertical (20).
 7. The touch fastener accordingto claim 1, wherein it consists at least partially of a plastic materialwhich can be processed by means of a micro-replication process.
 8. Thetouch fastener according to claim 3, wherein at least the contactsurface (22) of the head (12) consists of polyvinyl siloxane.
 9. Thetouch fastener according to claim 1, wherein the stem (14) actsoff-center on the head (12).
 10. A touch fastener element for a touchfastener according to claim 1, wherein it has a tapered stem (14) whichis coupled by means of an articulation part (16) to the head (12) in theform of a head plate which runs flat.